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8 HVAC Noises That Need Your Attention

How old is your HVAC unit? If it’s more than a few years old, it may be humming, clanking and squealing on occasion. What do those sounds mean? Should you be concerned? Or should you ignore them and hope they go away?

Some may be minor problems. Some you should never ignore. And in some cases, those minor problems can quickly escalate into very expensive nightmares. While some noises can indicate a minor repair, if you ignore it for too long it might lead to replacing instead of repair.

Here are eight sounds you should listen for and call a technician in immediately when you hear them.


This sound typically comes when a bolt is loose or a part is broken. The blades of the outdoor fan in your air conditioning unit or the indoor blower may be out of balance, causing them to hit other parts in your equipment. It may also be a sign of a failure in some other part in the sealed unit.


If you hear a buzzing noise, it’s usually an indication that debris is in either the indoor or outdoor unit, or the fan blades are out of balance. It can also mean that it is time to clean your air condenser or it’s time to change the air filter.


A humming noise can signal a loose part in the air conditioner. It may be centered in the refrigerant piping or a loose wire somewhere in the system. If you hear a humming in the compressor as it starts, or the unit won’t start, it might be the motor.


A rattling or banging sound is often heard when the motor or the blower inside your HVAC has a problem. Loud banging is usually an indication of a component coming loose. Rattling may also be heard if the blower is misaligned.


If a belt is wearing out, it can lead to a squealing noise coming from the blower. It’s wise to replace the belt before it cracks or breaks to avoid further extensive damage to the system.


A high pitched whistling coming from your air conditioner is a critical sound. It’s usually caused by leaking refrigerant. If you hear whistling, you should shut down your HVAC system and call in a technician immediately. It indicates internal pressure and can become hazardous if the blower isn’t shut down.


A clicking sound may be heard as the HVAC system is turned on and off. A repeated clicking is a faulty contactor. A failure in the electrical system or a wrong connection may be causing the problem.

Not sure what the noise coming from your HVAC system means? Give us a call, and we can inspect your entire system and make sure it is in good working condition before winter sets in.

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